The present application relates to information processing apparatuses, information storage media, content management systems, data processing methods, and computer programs. More specifically, the present application relates to an information processing apparatus, an information storage medium, a content management system, a data processing method, and a computer program which can achieve management for each segmented data unit of various contents requiring content use management and which can efficiently and reliably execute checking of content tampering.
Various types of software data (which are hereinafter referred to as “contents (content)”), such as audio data of music and so on, image data of movies and so on, game programs, and various application programs, can be stored, as digital data, in a storage medium. Examples of the storage medium include a Blu-ray disc using a blue laser, a DVD (digital versatile disc), an MD (mini disc), and a CD (compact disc). In particular, a Blu-ray disc using a blue laser is a high-density recordable disc and can record a large amount of video content as high-quality data.
Digital contents are stored in various information storage media (storage media) as described above and are supplied to users. The users use their own playback apparatuses, such as PCs (personal computers) and disc players, to play back and use the content.
For many contents, such as music data and image data, the creators or sellers thereof generally have distributorships and so on. Thus, for distributing the contents, generally, a certain use restriction is applied, that is, only authorized users are permitted to use the contents, to prevent unauthorized copying and so on.
The use of a digital recording apparatus and a storage medium allows recording and playback to be repeatedly performed without deterioration of, for example, video and audio. Thus, there are problems in that distribution of unauthorized copied contents through the Internet, circulation of the so called “pirated discs”, i.e., CD-R discs and so on containing copied contents, and use of copied contents stored on the hard disks of PCs and so on are rampant.
DVDs or large-capacity storage media, such as storage media utilizing a blue laser, that are under development in recent years allow a large amount of data of, for example, one to several movies to -be recorded as digital information to one medium. As the recording of video information and so as digital information becomes available, prevention of unauthorized copying and protection of copyright holders become increasingly important issues. Today, in order to prevent such unauthorized copying of digital data, various technologies for preventing illegal copying are actually incorporated into digital recording apparatuses and storage media.
For example, DVD players employ a content scramble system (content scramble system). In the content scramble system, video data, audio data, and so on are encrypted and are recorded to a DVD-ROM (read only memory) and a key used for decrypting the encrypted data is given to a licensed DVD player. The license is given to a DVD player designed to comply with predetermined operating rules specifying that, for example, no unauthorized copying is to be made. Thus, the licensed DVD player uses the given key to decrypt the encrypted data recorded in the DVD-ROM, thereby making it possible to play back video and audio from the DVD-ROM.
On the other hand, since a DVD player that does not have the license does not have a key for decrypting the encrypted data, it cannot decrypt the encrypted data recorded in the DVD-ROM. In this manner, in the configuration of the content scramble system, DVD players that do not satisfy conditions required for the licensing cannot play back the DVD-ROM in which the digital data is recorded, thereby preventing unauthorized copying.
As one scheme for eliminating unauthorized content use, a control configuration in which the presence/absence of content tampering is checked is proposed for an information processing apparatus (playback apparatus) for executing content playback. In the scheme, the content playback is permitted only when it is confirmed that the content is not tampered, and the content playback is executed when it is determined that the content has been tampered.
For example, Patent Document 1 discloses a control configuration in which hash values are calculated from a content file to be played back and are compared with prepared comparison hash values, i.e., with comparison hash values pre-calculated based on legitimate content data. When newly determined hash values match the comparison hash values, it is determined that the content has not been tampered and the process proceeds to content playback processing.
However, when processing for determining hash values based on a content is executed as described above and the amount of content data serving as source data for determining the hash values is large, a processing load and the amount of processing time required for the calculation become enormous. Today, as the quality of moving image data is enhanced, cases in which a data amount of several gigabytes to several tens of gigabytes per one content are increasing. When hash-value determination processing for a content based on a large amount of data is performed by user equipment for executing content playback, there are problems in that a data processing capability required for the user equipment is increased, the amount of time required for the content verification increases, and content playback processing cannot be efficiently performed.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2002-358011